The Lasker Trap is a chess opening

Chess opening

A chess opening is the group of initial moves of a chess game. Recognized sequences of opening moves are referred to as openings as initiated by White or defenses, as created in reply by Black. There are many dozens of different openings, and hundreds of named variants. The Oxford Companion to...

 trap

Chess trap

- List of chess traps :Ordered by chess opening:*Albin Countergambit – Lasker Trap*Blackmar-Diemer Gambit – Halosar Trap*Bogo-Indian Defence – Monticelli Trap*Budapest Gambit – Kieninger Trap...

 in the Albin Countergambit

Albin Countergambit

The Albin Countergambit is a chess opening that begins with the moves:and the usual continuation is:The opening is an uncommon defense to the Queen's Gambit. In exchange for the gambit pawn, Black has a central wedge at d4 and gets some chances for an attack...

, named after Emanuel Lasker

Emanuel Lasker

Emanuel Lasker was a German chess player, mathematician, and philosopher who was World Chess Champion for 27 years...

, although it was first noted by Serafino Dubois

Serafino Dubois

Serafino Dubois was an Italian chess player. He was known for his writings on the game and for his promotion of chess in Italy.-Chess career:Serafino Dubois was born in Rome...

 . It is unusual in that it features an underpromotion as early as the seventh move.
The Albin Countergambit begins with the moves:

1. d4 d5

2. c4 e5

3. dxe5 d4

The black pawn

Pawn (chess)

The pawn is the most numerous and weakest piece in the game of chess, historically representing infantry, or more particularly armed peasants or pikemen. Each player begins the game with eight pawns, one on each square of the rank immediately in front of the other pieces...

 on d4 is stronger than it appears.

4. e3?

Careless. Usual and better is 4.Nf3.

4... Bb4+

5. Bd2 dxe3!

(See diagram.) Now White's best option is to accept doubled pawns

Doubled pawns

In chess, doubled pawns are two pawns of the same color residing on the same file. Pawns can become doubled only when one pawn captures onto a file on which another friendly pawn resides. In the diagram, the pawns on the b-file and e-file are doubled...

 with 6.fxe3.

6. Bxb4??

Blundering

Blunder (chess)

In chess, a blunder is a very bad move. It is usually caused by some tactical oversight, whether from time trouble, overconfidence or carelessness. While a blunder may seem like a stroke of luck for the opposing player, some chess players give their opponent plenty of opportunities to blunder.What...

 into the Lasker Trap. In an 1899 consultation game in Moscow

Moscow

Moscow is the capital, the most populous city, and the most populous federal subject of Russia. The city is a major political, economic, cultural, scientific, religious, financial, educational, and transportation centre of Russia and the continent...

, Blumenfeld, Boyarkow, and Falk playing White against Lasker tried 6.Qa4+?, but Black wins after this move also. The game continued 6...Nc6 7.Bxb4 Qh4 8.Ne2 Qxf2+ 9.Kd1 Bg4 10.Nc3 0-0-0+ 11.Bd6 cxd6 12.e6 fxe6 13.Kc1 Nf6 14.b4 d5 15.b5 Ne5 16.cxd5 Nxd5 17.Qc2 Nb4 18.Nd1+ Nxc2 19.Nxf2 Rd2 White resigns.
The Encyclopedia of Chess Openings (volume D) gives 6.fxe3 as the relatively best move. Black gets a slight advantage, but White has avoided the worst and can defend.

6... exf2+

Now 7.Kxf2 would lose the queen

Queen (chess)

The queen is the most powerful piece in the game of chess, able to move any number of squares vertically, horizontally, or diagonally. Each player starts the game with one queen, placed in the middle of the first rank next to the king. With the chessboard oriented correctly, the white queen starts...

 to 7...Qxd1, so White must play 7.Ke2.

7. Ke2 fxg1=N+!

Underpromotion is the key to the trap. (If instead 7...fxg1=Q, then 8.Qxd8+ Kxd8 9.Rxg1 is okay for White.) Now 8.Rxg1 Bg4+ skewers White's queen, so the king

King (chess)

In chess, the king is the most important piece. The object of the game is to trap the opponent's king so that its escape is not possible . If a player's king is threatened with capture, it is said to be in check, and the player must remove the threat of capture on the next move. If this cannot be...

 must move again.

8. Ke1 Qh4+

If White tries 9.g3 then the fork

Fork (chess)

In chess, a fork is a tactic that uses a single piece to attack multiple pieces at the same time. The attacker usually hopes to gain material by capturing one of the opponent's pieces. The defender often finds himself in a difficult position in which he cannot counter all threats. The attacking...

 9...Qe4+ wins the rook

Rook (chess)

A rook is a piece in the strategy board game of chess. Formerly the piece was called the castle, tower, marquess, rector, and comes...

on h1.

9. Kd2 Nc6

White is hopelessly lost. After 10.Bc3 Bg4 followed by 11...0-0-0+ is crushing.